This invention is generally directed to toner and developer compositions and to processes for the preparation thereof. More specifically, the present invention is generally directed to toner compositions comprised of toner particles containing an encapsulated component with a silicone oil therein. More specifically, the aforementioned toner compositions are comprised of toner resin particles and pigment particles that function as an encapsulating material for domains of certain polymers having entrapped therein mineral oils, silicone oils, or other similar release components. Moreover, the toner and developer compositions of the present invention can contain therein charge enhancing additives for the primary purpose of imparting positive charges to the toner resin particles enabling the use of these compositions in imaging systems wherein the photoresponsive imaging member is negatively charged. In addition, there can be added to the toner and developer compositions of the present invention other components such as colloidal silicas, metal salts of fatty acids or metal salts. The toner and developer compositions of the present invention are useful for affecting the development of images in electrophotographic imaging systems, and wherein the components associated with silicone oils are not required since the release agent is incorporated into polymer resin particles.
Numerous toner and developer compositions are known inclusive of those with waxes therein, reference for example British Pat. No. 1,442,835. The aforementioned patent illustrates toner compositions comprised of a styrene homopolymer or copolymer resin, and at least one polyalkylene compound. According to the disclosure of this patent, reference page 2, beginning at line 90, the starting polymer resin may be either a homopolymer of styrene, or a copolymer of styrene with other unsaturated monomers, specific examples of which are disclosed on page 3, beginning at line 1. Polyalkylene compounds selected for incorporation into the toner compositions disclosed in this patent include those of a low molecular weight, such as polyethylene, and polypropylenes of an average molecular weight of from about 2,000 to about 6,000.
Additionally, there is disclosed in U.S. Pat. No. 4,460,672, entitled "Positively Charged Toner Compositions", a developer composition mixture comprised of electrostatic toner particles consisting of resin particles, pigments particles, low molecular weight waxy materials with a molecular weight of from about 500 to about 20,000; and further included in the composition from about 0.5 percent by weight to about 10 percent by weight of a charge enhancing additive selected from, for example, alkyl pyridinium halides, organic sulfonate compositions, and organic sulfate compositions. The disclosure of this patent is totally incorporated herein by reference.
Also, there is disclosed in U.S. Pat. No. 4,206,247 a developer composition comprised of a mixture of resins including a low molecular weight polyolefin and alkyl modified phenol resins. More specifically, it is indicated in this patent, reference column 4, line 6, that the invention is directed to a process which comprises the steps of developing an image with toner particles containing in certain proportions at least one resin selected from group B, wherein the resins of group A include a low molecular weight polyethylene, a low molecular weight polypropylene, and similar materials; and wherein the group B resins include natural resin modified maleic acid resins, and natural modified pentaerythritol resins. As examples of group A resins there are mentioned polystyrene, styrene series copolymers, polyesters, epoxy resins, and the like, reference the disclosure in column 5, line 47. The molecular weight of the polypropylene or polyethylene used is from about 1,000 to about 10,000, and preferably from about 1,000 to about 5,000.
Moreover, developer compositions with charge enhancing additives, especially additives which impart a positive charge to the toner resin, are well known. Thus, for example, there is described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica. Additionally, in U.S. Pat. No. 3,893,935 there is described the utilization of certain quaternary ammonium salts, which when incorporated into a toner material, were found to provide a positive toner charge when mixed with a suitable carrier vehicle. There is also described in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions comprised of resin particles and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds and their hydrates. Examples of alkyl pyridinium compounds disclosed in the '672 patent include cetyl pyridinium chloride. Also, there is illustrated in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, positively charged developer compositions containing organic sulfate, and sulfonate compositions as charge enhancing additives.
In addition, there is illustrated in U.S. Pat. No. 4,517,272 electrostatic dry toner compositions comprising finely divided polymeric particles admixed with a silicone oil, reference for example, column 1, beginning at line 62, and continuing on to column 2, line 65. This patent, however, does not teach the utilization of an encapsulated toner thereby preventing undesirable agglomeration of the toner particles. Also, with respect to the '272 patent, there is no teaching therein with respect to the addition of large amounts of silicone oil to the toner composition, that is amounts exceeding 5 percent and up to 80 percent, and preferably from about 30 to about 50 percent as is the situation with the toner compositions of the present invention. Moreover, of interest are U.S. Pat. Nos. 3,485,787 directed to elastomeric compositions with hydrogenerated black copolymers and oils; 4,050,053 directed to polymer oils in carbon black master batches; and 4,357,406 disclosing developers for electrophotography comprising a continuous phase consisting of a homogeneous mixture of a resin and a pigment, and a dispersed phase consisting of spherical particles of a soft parting or fixing material of an emulsion dispersed in the continuous phase, reference the Abstract of the Disclosure.
Developer compositions can be selected for use in developing electrostatic images, wherein the toner image is fixed to a permanent substrate such as paper by contacting the paper with a roller, the surface of which is formed from a material capable of preventing toner particles from sticking thereto. In this process, however, the surface of the heated fixing roll is brought into contact with the toner image, thus a part of the toner image can adhere to and remain on the surface of the roll. This causes a part of the toner image to be transferred to the surface of a subsequent sheet on which the toner image is to be successively fixed, thereby causing the well known undesirable offset phenomena.
In order to substantially eliminate offsetting, and more specifically for the purpose of preventing adhesion of the toner particles to the surface of the fixing roller, there have been selected certain types of rollers, the surface of which may be covered with a thin film of an offset preventing liquid such as a silicone oil. These oils are highly effective, however, the apparatus within which they are incorporated is complicated and costly since, for example, a means for feeding the oil is required. Also, not only do the silicone oils emit an undesirable odor, but these oils deposit on the machine components causing toner particles to undesirably collect on, and adhere to the silicone oils. An accumulation of toner particles on machine components is troublesome in that image quality is adversely effected, and further these components must be periodically cleaned and/or replaced adding to the maintenance costs of the machine system involved.
Accordingly, there is a need for toner and developer compositions that can be selected for xerographic imaging apparatuses wherein silicone oil release devices are avoided. Additionally, there is a need for improved toner and developer compositions with stable triboelectric charging characteristics, and wherein offsetting is substantially avoided. There also is a need for improved toner and developer compositions which can be selected for the development and fixing of electrostatic latent images in electrophotographic imaging processes wherein the toner particles utilized are substantially free of agglomeration. Furthermore, there is a need for toner and developer compositions comprised of resin particles which have incorporated therein a release agent thereby preventing the release oil from migrating within the machine environment. There also remains a need for toner compositions which will not agglomerate or stick together when a release agent such as a mineral oil or silicone oil is included therein. Furthermore, there is a need for encapsulated, nonsticky toner compositions containing a host resin, and encapsulated therein a component with a mineral oil or silicone oil; and wherein there results subsequent to development of images the absence of any undesirable oil on the final copy.